Telephone trunking system.



PATENTED JAN..' 22, 1907.

W. W. DEAN. TELEPHONE TRUNKING SYSTEM.

APPLIOATION FILED FEB, 6. 1903.

UNITED STATES PATENT orricn WILLIAM W. DEAN, OF CHICAGO, ILLINOIS, ASSIGNOR TO KELLOGG SWITCHBOARD AND SUPPLY COMPANY, OF CHICAGO, ILLINOIS, A

CORPORATION OF ILLINOIS.

T ELEPHONE TRUNKING SYSTEM.

Specification of Letters Patent.

Patented Jan. 22, 1907.

Application filed February 6, 1903. Serial No. 142,114.

To a whom it may concern.-

Be it known that I, WILLIAM W. DEAN, a citizen of the United States of America, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvementin Telephone Trunking Systems, of which the following is a specification.

In an application filed by me June 28, 1902, Serial No. 113,581, I have shown and described a telephone trunking system in which a relay serving to disconnect the test-relay and place the tip-strand of the trunk-cord in condition for conversation is actuated over a portion of the talking-circuit when the trunkcord is connected with the called line. In a second application, filed January 22, 1903, Serial No. 140,166, I have shown a similar trunking system in which an auxiliary relay is employed for this purpose, said relay being initially actuated by the ringing-key when a wanted subscriber is called and thereafter controlled by the connection of the trunkcord with the said line.

' My present invention relates to the same general trunking system asthe said latter application and employs likewise an auxiliary relay; but the energization of said. relay after the subscriber is called is controlled from the outgoing end of the trunk and by the condition of the wanted-subscribers telephone.

My invention is illustrated in the accompanying drawing, in which the figure represents a diagram of a trunking system embodying my improvements.

L indicates a subscribers line of the wellknown two-wire or Dunbar type extending from a subscribers station A to a central otfice C, where a suitable opera'tors outfit is shown for the purpose of connecting the lines together for conversation and also for connecting the lines with the trunks, such as D, extending from the station C to another station C At the latter station are lines of the same type as indicated at L upon which subscribers stations E and F are located.

At the station C the trunk-relay r is proing-key and is thereafter controlled through its spring 6 and forward contact, the conductor 7, spring 8 of the trunk-relay forward contact, and the wire 9, leading to the live pole of the said battery. In order that this trunkrelay shall be energized throughout the connection, it is necessary that the trunk-relay be also actuated during the connection,-which is accomplished by the low-resistance winding thereof in circuit with the tip-relay. The subscriber located upon the line L desiring a connection takes up her receiver and permits current from the battery B to fiow over the telephone-line and through the line relay R, which serves to close a circuit of the line-signal S. The operator observing the signal inserts the answering-plug P of her cord-circuit and depresses springs 10 of her listening-key to connect her instrument with the cord-circuit to receive the order. Supervisory signal S isnow extinguished by the operation of both supervisory relays r and 1. Upon ascertaining that a subscriber at the branch exchange is wanted, the callingvisory relay 7" and over the sleeve-strand of the cord and through the retardation-coil 12,

-which causes the actuation of said relay to disconnect the test-relay 1", associated with the cord, and to complete the ti -strand for talking through the s ring 13 of said relay. The supervisory signa S 18 also operated to indicate that the wanted subscriber has not yet responded. The actuation of tip-relay 1", associated with the cord-circuit, 1s prevented by reason of the high-resistancewinding 2 of the trunk relay at the ofl ice C since it is included in the metallic circuit of the trunk and the calling end of the cord circuit. The insertion of the plug P of the trunk-cord actuates the cut-oif relay R of the line L to render the line-signal S inoperative and to connect the external line-circuit spring 24 of a locking-relay r. 40.

with the switchboard-circuit of the line. If the subscriber F is the one desired, the springs 5 and 14 of the ringing-key are actuated, which serves to connect the generator 15 with the tip side of the line and to send current through the ringer at the station F, which is connected with the tip side of the line. The cut-off relay -R is maintained actuated by current from battery 13 over the battery-lead 16 and through conductor 17 when the sleeve-spring 14 of the ringing-key is depressed. The spring 5 of said key also serves to close a path for current from the 1 battery B over conductor 16, through resistance 18 in the wire 19, spring 5, conductor 20, and through auxiliary relay r to ground. The actuation of this relay closes a lockingcircuit for itself through spring 6, conductor 7, spring 8 of the trunk-relay, which is now energized, and conductor 9 to battery B This auxiliary relay remains actuated, there fore, after the ringing-key is returned to normal (position and the spring 5 thereof re lease The auxiliary relay 1' is provided with an additional spring 21, serving in its forward position to complete the tip-strand t of the trunk-cord, but 1n its normal position to connect with a conductor 22, leading to a grounded high-resistance and high-impedance test-relay r. The sleeve-relay r at the incoming end of the trunk is now energized from the battery B over the sleevestrand .9 of the trunk-cord. This relay, through its spring 23 and forward contact, closes a path for current from the battery B -through the ringing-lamp S, the circuit of which is completed at the back contact and This light indicates to the trunk-operator that the called subscriber has not yet responded.

The response of the called subscriber permits current from the battery B to flow over the sleeve-strand of the trunk-cord, the sleeveconductor of the telephoneline, and thence back to the central office over the tip side of the line and the tip-strand of the cord and thence through conductor 25, the low-resist ance winding of the trunk-relay 1", and through the tip-relay r to ground. The current in this path actuates said tip-relay, with the result that the high-resistance winding 2 of the trunk-relay is short-circuited by its spring 26 and forward contact, thus removing said high resistance from the outgoing end of the trunk and permitting sufficient current over the metallic circuit thereof to operate the tip supervisory relay 1" in the office C to eXtinguish the supervisory lamp S This indicates to the A operator that the called subscriber has responded. The flow of current through thelow-resistance winding 3 of the trunk-relay prevents demagnetization of the same, so that the auxiliary relay r is not released. The spring 27 of tip-relay r now completes, through its forward contact and conductor 28, the circuit of locking-relay 7*, which is energized from the battery B and serves, first, to open the circuit of ringinglamp S, thereby extinguishing it and indicating to the B operator that the wanted subscriber has responded, and, secondly, to close, through the forward contact of said spring, a locking-circuit for itself, whereby it remains actuated throughout the connection or as long as the trunk-relay is actuated. At the termination of the conversation the subscribers return their receivers to their hooks, thereby opening the line-circuits and in the case of line L lighting the supervisory lamp S In the case of line L tip-relay r is deprived of current, and the short circuit of the high-resistance winding 2 of relay 1 is broken, and the said high resistance reinserted in the metallic circuit of the outgoing end of the trunk, which results in depriving suvervisory relay r at the A office of operating current, and the supervisory signal S is lighted. Upon observing both supervisory signals the A operator withdraws the plugs and takes down the connection, thus restoring all parts to normal condition at her ofiice. The withdrawal of the cord-circuit from the outgoing end of the trunk entirely deprives the trunk-relay of operating-current, which allows its spring 29 to engage its back grounded contact, and thereby closes its circuit for the disconnecting-lamp S over the conductor 30, spring 31 of sleeve-relay 1" its forward contact, and conductors 32 and 33 and through the pilot-relay r and the battery B to ground. The operator observing the pilot-signal S and the disconnect-signal S knows that the trunk has been disconnected at the outgoing end and that it is time to withdraw the trunk-plug, which is accordingly done.

If the station E upon the line L had been wanted, the trunk-operators would have depressed the springs 4 and 34 of the ringingkey, which would have accomplished the same results, as before described, so far as the operation of the relays is concerned, and the ringing-current would have been sent out over the sleeve side of the line to ring the bell at station E. Before the trunk-plug is connected with the called line the said line is tested in the usual way by touching the tip of the plug to the test-rings thereof, which if the line is busy permits a flow of current over the tip-strand and through the said test-relay r". This relay is then actuated and ca ses a click in the operators receiver. Any other test-responsive device or arrangement of the test-receiving circuits may of course be employed. In case the calls to the office 0 are infrequent it may be desired to dispense with the order-circuit 11 and'use the trunk for communication between the operators. In this method of working the A operator would first test the idle or busy condition of the trunk and insert the calling-plug in one that is idle. erating the trunk-relay 1* while the sleeve-relay r is dcenergized, so that a path for current from the battery B will be completed .through the pilot-relayr, conductor 33, forward contact and spring 29 of the trunk-relay, conductor 30, through lamp S and spring 31 and back contact to ground, thus lighting the lamp 8", which now serves as a calling-signal to the B operator. In response to this signal the B operator connects her telephone with the trunk and receives the order ,for connection from the A operator. The insertion of the trunk-plug in response'to this order actuates the-sleeve-relay r and severs the calling-lamp circuit. The remainder of the connection and disconnection i the same as that before described. l'

It will be understood that the ringing-' keys and listening-keys mentioned may be of any usual type, preferably such as operate simultaneously the desired springs by the actuation of a single lever or key.

Having thus described my invention, what I claim, and desire to secure by Letters Patent, is

1. In a telephone trunking system, the combination with a testing outfit at the incoming end, a relay to control the connection of said outfit with said end of the trunk, means to control said relay from the outgoing end of the trunk and from the calledsubscribers line, and means to initially energize said relay in calling the wanted sub scriber, substantially as described.

2. In a telephone trunking system, the combination with a telephone-line, of testing apparatus to determine the idle or busy condition of the line, a relay to control said. testing apparatus, means to initially energize said relay in the actuation of the ringingkey, and means to control the further actuation of said relay from the outgoing end of the trunk, substantially as described.

3. In a telephone trunking system, the combination with a telephone-line, of a test: ing apparatus associated with the incoming end of the trunk, a relay to disconnect the testing apparatus from the incoming end of the trunk during conversation, means toinitially operate said relay, and further means to control its actuation from the outgoing end of the trunk, substantially as de scribed.

4. In a telephone trunking system, the combination with a tel ephone-line, of testing apparatus associated with the incoming end. of the trunk, a relay to control said testing apparatus, means to first operate said relay, and further means to control the actuation of saidrelay from the outgoing end of the trunk and. a called-subscribers station, substantially as described.

This would result in op .5. In a telephone trunking system, the combination with a telephone-line, of testing apparatus associated with the incoming end of the trank, a relayto control said apparatus, said relay being initially operated in the act of calling the wanted subscriber and thereafter controlled by the connection with the outgoing end of the trunk and by the called subscriber, substantially as described.

6. In a telephone trunking system, the combination with a telephone-line, of testing apparatus at the incoming end of the trunkline, a relay at said end, means associated with the ringing-key for operating said relay for disconnecting said apparatus when the wanted party is called, and further means for maintaining the actuation of said relay until the answering subscriber has replaced hisreceiver upon the hook and the connection has been severed with the outgoing end. of the trunk, substantially as described.

7. The combination with v a telephone trunk-circuit adapted to connect lines together for conversation, of a relay the actuation of which completes the tip-strand of said trunk-circuit for talking purposes, a lockingcircuit for said relay, asignal-circuit, asecond relay the actuation of which opens said signalcircuit, a locking-circuit for said second relay, and a trunk-relay'the demagnetization of which breaks each of said locking-circuits, substantially as described.

8. In a telephone system, the combination with a telephone-line, of a trunking circuit, a testing system for said line, a relay with normal contacts connecting said testing system with the trunking circuit and means not associated with said line for actuating said relay to disconnect said testing system, and means associated with the line for reconnecting said testing system, substantially as described.

9. In a telephone system, the combination with a telephone-line, of a trunking circuit, a testing system for said line, a relay with normal contacts connecting said testing system with the trunking circuit, means to actuate said relay, a locking-circuit for said relay, and means actuated ,over both ends of said trunking circuit for severing the locking-circuit of said relay, substantially as described.

10. In a telephone system, the combination with a telephone-line, of a trunking circuit, a testing system for said line, a relay with normal contacts connecting said testing system with the trunking circuit, means to actuate said relay, a locking-circuit for said system with the trunking circuit, means to actuate said relay, a locking-circuit for said relay, and means depending upon the condition of the called-subscribers telephone for severing said lockingcircuit, substantially as described.

12. In a telephone system, the combination with a cord-circuit and a telephone-line, of a trunking circuit adapted to connect the two for conversation, a testing system for said line, a relay with normal contacts connecting said testing system with the trunking circuit, means to actuate said relay to sever said connection, a locking-circuit for said relay, and means depending, upon the condition of the called-subscribers telephone and the connection of said cord-circuit with the trunk for severing said locking-circuit, substantially as described.

13. In a telephone system, the combination with a cord-circuit and a telephone-line, of a trunking circuit adapted to connect the two. for conversation, a testing system for said line, a relay with normal contacts connecting said testing system with the trunking circuit, means to actuate said relay to sever said connection, a locking-circuit for State of Illinois, this 30th day of January, 1903.

WILLIAM W. DEAN. Witnesses:

ROBERT LEwIs AMES, GAZELLE BEDER. 

